Process for synthesis of diamond by CVD

ABSTRACT

A synthesizing process for diamond by the chemical vapor phase growth method, characterized by converting an organic compound containing carbon, hydrogen and at least one of oxygen and nitrogen, to a gas phase, mixing the gas with hydrogen gas, decomposing the mixed gas by an energy of heat, electron beam, light, direct current glow discharge, alternating current glow discharge, or direct current arc discharge, and introducing the decomposed gas to the surface of a heated substrate (5) to deposit diamond on the surface of the substrate.

TECHNICAL FIELD

The present invention relates to a process for the synthesis of diamondby the chemical vapor phase growth method.

BACKGROUND ART

Previously known processes for the synthesis of diamond are classifiedas follows according to the starting material.

(1) Hydrocarbon is used as the raw material

The chemical vapor phase deposition method for decomposing a gas by anenergy of heat, electron beam, plasma or the like to form carbon atomsin an activated state and deposit diamond on a substrate.

(2) Graphite is used as the starting material

1. The ion beam method for forming positive ions of carbon from graphiteaccording to the discharge technique, accelerating and focusing the ionsand causing the accelerated and focused ions to impinge against thesurface of a substrate to deposit diamond thereon.

2. The chemical transportation method for locating graphite, hydrogenand a substrate in a sealed reaction tube, placing graphite at ahigh-temperature portion and the substrate at a low-temperature portion,applying an energy of heat or the like to the hydrogen gas to generateatomic hydrogen and depositing diamond on the surface of the substrate.

According to the above-mentioned chemical gas phase deposition method(1), a diamond film can be formed at a growing speed of 0.1 to 3 μm perhour on the surface of the heated substrate if the operation is carriedout under a reduced pressure (10 to 100 Torr) at a hydrocarbonconcentration of 0.1 to 1.0%. However, this method is defective in thatthe range of the conditions for the synthesis of diamond is narrow, adeposition of graphite or non-diamond carbon often occurs and thediamond deposition speed is low. Especially, in case of hydrocarbonswhich consist solely of carbon and hydrogen, the kinds of usablestarting materials are limited.

The above-mentioned ion beam method (2)-1 is advantageous in thatdiamond can be deposited on the surface of the substrate at normaltemperature, but is defective in that an ion beam-generating apparatusand a focusing apparatus are expensive, the atom of an inert gas usedfor the discharge is trapped in the diamond film, and i-carbon isdeposited simultaneously with diamond.

Since the above-mentioned chemical transportation method is a closedtube method in which a hydrocarbon formed by the reaction betweengraphite and atomic hydrogen in the closed tube is utilized, acontinuous operation is impossible and the thickness of a diamond filmthat can be synthesized is limited. The method is also defective in thatthe diamond synthesis conditions such as the concentration of thereaction gases and the heating temperature cannot be independentlycontrolled.

In the process disclosed in Japanese Examined Patent Publications No.59-27753 and No. 59-27754, in which diamond is synthesized by usinghydrogen and a hydrocarbon alone, the kinds of applicable starting gasesare extremely limited, and the gases that can be practically used aremethane, ethane, and ethylene alone.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to obviate the above-mentioneddefects of the conventional methods and provide a process for thesynthesis of diamond in which the range of the diamond synthesisconditions is broad, the apparatus and starting material used are notexpensive, a great number of kinds of gases can be used as the startinggas, and diamond having a high quality can be obtained at a highdeposition speed.

According to the present invention, an organic compound containingoxygen and/or nitrogen in addition to carbon and hydrogen (sometimesreferred to merely as "organic compound" hereinafter) is converted to agas phase and mixed with hydrogen gas, the mixed gas is decomposed by anenergy of heat, electron beam, light, or plasma of a direct current glowdischarge, or an alternating or direct current arc discharge, to form amethyl group and atomic hydrogen, and the decomposed gas is introducedto the surface of a substrate heated at 500° to 900° C. to depositdiamond thereon, whereby the above-mentioned object can be attained.Namely, the most significant feature of the present invention resides ina discovery of an appropriate condition for synthetizing diamond with acombination of a starting material which consists of an organic compoundcontaining an oxygen or nitrogen atom (the above-mentioned, methanol,ethanol, acetone, methylamine and the like) and an energy-impartingmeans.

Typical organic compounds that can be used in the present invention aredescribed below.

(I) O-Containing Organic Compounds

Alcohol group (--OH)

C₂ H₂ OH:ethanol

CH₃ OH:methanol

(CH₃)₂ CHOH:2-propanol

(CH₃)₃ COH:2-methyl-2-propanol

CH₃ --CH₂ --CH₂ OH:1-propanol

(CH₃)₂ --C(OH)CH₂ COCH₃ :diacetone alcohol

CH₂ ═CHCH₂ OH:allyl alcohol

Ether group (--O--)

CH₃ OCH₃ :dimethyl ether

CH₃ CH₂ --O--CH═CH₂ :ethoxyethylene

CH₃ --O--CH₂ CH₃ :ethylmethyl ether

(CH₃ CH₂)₂ O:diethyl ether ##STR1## 2,3-epoxybutane (CH₃ COO)₂ O:acetylether

Ketone group (C═O)

CH₃ COCH₃ :acetone

(II) N-Containing Organic Compounds

Amine (RNH₂)

CH₃ NH₂ :methylamine

CH₃ CH₂ NH₂ :ethylamine

(CH₃)₂ NH:dimethylamine

(CH₃)₃ N:trimethylamine

(CH₃)₂ CHNH₂ :isopropylamine

CH₃ COC₂ H₅ :ethylmethyl ketone

C₂ H₅ COC₂ H₅ :diethyl ketone

CH₃ COCH₂ COCH₃ :2,4-pentane-dione

C₆ H₅ COCH₃ :acetophenone

C₁₀ H₇ COCH₂ CH₂ CH₃ :1'-butyronaphthone

Ester (RCOOR')

CH₃ COOCH₃ :methyl acetate

CH₃ COOC₂ H₅ :ethyl acetate

CH₃ COOC₅ H₁₁ :isoamyl acetate

Ketene group

(CH₃)₂ C═CO:dimethyl ketene

C₆ H₅ --CH═CO:phenyl ketene

Acetyl group (CH₃ CO--)

CH₃ COOH:acetic acid

(CH₃ CO)₂ O:acetic anhydride

CH₃ COC₆ H₅ :acetophenone

(CH₃ CO)₂ :biacetyl

Aldehyde group (--CHO)

HCHO:formaldehyde

CH₃ CHO:acetaldehyde

C₂ H₃ CH₂ CHO:propionaldehyde

    ______________________________________                                        Peroxide bonding (--O--O--)                                                   ______________________________________                                        (CH.sub.3).sub.3 COOH                                                                          tert-butyl hydroxyperoxide                                   ((CH.sub.3).sub.3 CO).sub.2                                                                    di-tert-butylperoxide                                        CH.sub.3 OOH     methyl hydroxyperoxide                                       (CH.sub.3).sub.3 COOCOCH.sub.3                                                                 tert-butyl peroxide acetate                                  (CH.sub.3).sub.2 CHOOCH.sub.3                                                                  isopropyl methyl peroxide                                    CH.sub.3 COOC.sub.2 H.sub.5                                                                    methyl ethyl ketone peroxide                                 CH.sub.3 COOOH   peracetic acid                                               ______________________________________                                    

CH₃ COCH₃ :acetone

(II) N-Containing Organic Compounds

Amine (RNH₂)

CH₃ NH₂ :methylamine

CH₃ CH₂ NH₂ :ethylamine

(CH₃)₂ NH:dimethylamine

(CH₃)₃ N:trimethylamine

(CH₃)₂ CHNH₂ :isopropylamine

Nitrile group

CH₃ CN:acetonitrile

C₆ H₅ CN:benzonitrile

CH₂ ═CHCN:acrylonitrile

(CH₃)₃ CCN:pivalonitrile

Amide group

CH₃ (CH₂)₄ C--NH₂ :hexanamide

CH₃ CONH₂ :acetamide

Nitro group

C₂ H₅ NO₂ :nitroethane

CH₃ NO₂ :nitromethane

C₆ H₅ NO₂ :nitrosobenzene

C₃ H₇ NO₂ :nitropropane

The present invention is divided into two aspects according to theorganic compound used.

It is considered that the principle of the process of the presentinvention is probably as follows.

In the present invention, a mixed gas of an organic compound asmentioned above and hydrogen is decomposed by an energy of heat,electron beam, light, plasma of a glow discharge, or plasma of a director alternating current arc discharge (hereinafter referred to as theplasma) to generate a methyl group and atomic hydrogen. This methylgroup maintains a diamond type structure on the heated substrate surfaceand prevents double and triple bonds of other carbon atoms. Atomichydrogen is bonded with graphite or non-diamond carbon to form ahydrocarbon and the atomic hydrogen is removed in the form of thehydrocarbon. Accordingly, the atomic hydrogen exerts a function ofcleaning the substrate surface.

In order to synthesize diamond under temperature and pressure conditionsat which graphite is thermodynamically stable, it is necessary tomaintain the active states of the chemically active methyl group andatomic hydrogen. Furthermore, in order to form a diamond film, it isnecessary to supply a reaction energy sufficient to produce a diamondtype structure.

In the process of the present invention, in order to prevent adeposition of graphite or non-diamond carbon, preferably the mixingratio of the organic compound/hydrogen is not more than 1, and in orderto synthesize granular or filmy diamond, it is especially preferred thatthe above-mentioned mixing ratio be not more than 0.04.

In order to form a methyl group and atomic hydrogen by thermaldecomposition, preferably the temperature of a heating member is atleast 1500° C., more preferably from 2000° to 2800° C. As the heatingmember, there can be mentioned, for example, filaments of tungsten,molybdenum, tantalum and alloys thereof.

The pressure in the reaction tube where the substrate is placed is 0.01to 1000 Torr, preferably 100 to 800 Torr.

In order to form a methyl group and atomic hydrogen by decomposition byelectron beam, the current density of the electron beam applied to thesurface of the substrate is at least 1 mA/cm².

In order to form a methyl group and atomic hydrogen by decomposition bylight, preferably the wavelength of the light is not more than 600 nm,especially not more than 350 nm for the methyl group, and not more than85 nm.

In order to form a methyl group and atomic hydrogen by decomposition byplasma, preferably the power density of discharge is not less than 1W/cm².

An ordinary direct current or alternating current high frequency ormicrowave plasma discharge can be used for decomposition by plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a systematic diagram illustrating an example of the apparatusfor synthesizing diamond by thermal decomposition according to theprocess of the present invention;

FIG. 2 is a diagram illustrating a main part of an example of theapparatus for synthesizing diamond by electron beam decompositionaccording to the process of the present invention;

FIG. 3 is a diagram illustrating a main part of an example of theapparatus for synthesizing diamond by light decomposition according tothe process of the present invention;

FIG. 4 is a diagram illustrating a main part of an example of theapparatus for synthesizing diamond by plasma decomposition according tothe process of the present invention;

FIG. 5 is a photograph showing the reflection electron beam diffractionpattern of diamond obtained in Example 1 of the first aspect of thepresent invention;

FIGS. 6 and 7 are scanning type electron microscope photographs of thesurface and section of diamond obtained in Example 1 of the first aspectof the present invention; and,

FIG. 8 is a scanning type electron microscope photograph of granulardiamond obtained in Example 3 of the first aspect of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 through 4 illustrate examples of the apparatus for synthesizingdiamond according to the process of the present invention. Morespecifically, FIG. 1 is a systematic view of the process utilizing thethermal decomposition, FIG. 2 is a view showing a main part in theprocess utilizing the decomposition by electron beam, FIG. 3 is adiagram illustrating a main part in the process utilizing the lightdecomposition, and FIG. 4 is a diagram illustrating a main part in theprocess utilizing the plasma decomposition.

In FIG. 1, reference numeral 1 represents a device for supplying anorganic compound and hydrogen, reference numeral 2 represents a heatingfurnace, reference numeral 3 represents a substrate supporting stand,reference numeral 4 represents a reaction tube, reference numeral 5represents a substrate, reference numeral 6 represents a tungstenfilament, reference numeral 7 represents an exhaust apparatus, referencenumeral 8 represents an exhaust opening, and each of reference numerals9, 10, 11, and 12 represents a cock. At first, the substrate 5 is set onthe substrate supporting stand 3 in the reaction tube 4, and air in thereaction tube 4 is removed by the exhaust device 7. Then theconcentration and flow rate of the mixed gas are adjusted by the cocks10, 11 and 12, the mixed gas is introduced into the reaction tube 4, andthe pressure in the reaction tube 4 is maintained at a predeterminedlevel by the cock 9. The mixed gas is introduced into the reaction tube4 from the upper portion and is passed through the tungsten filament 6located in the vicinity of the substrate supporting stand 3, and themixed gas is supplied to the surface of the substrate 5. The heatingfurnace 2 and tungsten filament 6 are heated to predeterminedtemperatures.

A body of metal, e.g., Si or the like, of sintered ceramic, e.g., SiC,or a granular SiC or the like, is used as the substrate 5.

FIG. 2 illustrates the surrounding portion of the reaction tube 4; theother portion is omitted. In FIG. 2, reference numeral 13 represents adirect current power source for generating the electron beam between thetungsten filament 16 and the substrate.

The same members as the members shown in FIG. 1 are represented by thesame reference numerals. In FIG. 3, reference numeral 14 represents alight source and reference numeral 15 represents a light transmittingwindow, and in FIG. 4, reference numeral 16 represents a plasmagenerating power source and reference numeral 17 represents anelectrode.

EXAMPLE 1

A surface-polished silicon wafer was used as the substrate 5 and agaseous mixture comprising acetone (CH₃ COCH₃) and hydrogen at a ratioof 1:50 (volume ratio) was used as the reaction gas. The pressure in thereaction tube 4 was adjusted to 100 Torr. The substrate was heated to650° C. and the tungsten filament 6 was heated to 2000° C., and thegrowth was carried out for 1 hour. A deposition of filmy diamond havinga thickness of about 20 μm on the substrate 5 was observed. The Vickershardness of the obtained filmy diamond was 9500 to 12000 kg/mm², whichis substantially equal to the value of natural diamond. A reflectionelectron beam refraction pattern of the filmy diamond is shown in FIG.5. From this diffraction pattern, it was identified that the filmydiamond was cubic diamond. FIG. 6 is a scanning electron microscopephotograph showing the surface of the filmy diamond and FIG. 7 is ascanning type electron microscope photograph showing the section of thefilmy diamond.

EXAMPLE 2

A surface-polished silicon wafer was used as the substrate 5 and agaseous mixture comprising acetone (CH₃ COCH₃) and hydrogen at a mixingratio 1:100 (volume ratio) was used as the reaction gas. The pressure inthe reaction tube 4 was adjusted to 760 Torr (atmospheric pressure) andthe growth was carried out for 1 hour at a substrate temperature of 600°C. while the tungsten filament 6 for the thermal decomposition washeated to 2000° C. A deposition of filmy diamond having a thickness ofabout 20 μm on the substrate 5 was observed.

EXAMPLE 3

A mirror-polished silicon wafer was used as the substrate 5 and agaseous mixture comprising acetone (CH₃ COCH₃) and hydrogen at a mixingratio of 1:100 (volume ratio) was used as the reaction gas. The pressurein the reaction tube 4 was adjusted to 100 Torr and the growth wascarried out for 1 hour at a substrate temperature of 650° C. while thetungsten filament 6 was heated to a temperature of 2000° C. A depositionof granular diamond having a particle size of about 20 μm on thesubstrate 5 was observed. FIG. 8 is a scanning type electron microscopephotograph of the obtained granular diamond.

EXAMPLE 4

A surface-polished silicon wafer was used as the substrate 5 and agaseous mixture comprising methyl acetate (CH₃ COOCH₃) and hydrogen at amixing ratio of 1:500 (volume ratio) was used as the reaction gas. Thepressure in the reaction tube 4 was adjusted to 50 Torr and thesubstrate temperature was adjusted to 750° C., and the growth wascarried out for 1 hour while the tungsten filament 6 was heated to atemperature of 2000° C. A deposition of filmy diamond having a thicknessof about 10 μm on the substrate 5 was observed.

EXAMPLE 5

A surface-polished silicon wafer was used as the substrate 5 and agaseous mixture comprising methanol (CH₃ OH) and hydrogen at a mixingratio of 1:100 (volume ratio) was used as the reaction gas. The pressurein the reaction tube 4 was adjusted to 50 Torr and the substratetemperature was adjusted to 700° C. The growth was carried out for 1hour while the tungsten filament 6 was heated to a temperature of 2000°C. A deposition of filmy diamond having a thickness of about 3 μm on thesubstrate 5 was observed.

EXAMPLE 6

A surface-polished silicon wafer was used as the substrate 5 and agaseous mixture comprising ethanol (C₂ H₅ OH) and hydrogen at a mixingratio of 1:500 (volume ratio) was used as the reaction gas. The pressurein the reaction tube 4 was adjusted to 40 Torr and the substratetemperature was adjusted to 600° C. The growth was carried out for 1hour while the tungsten filament 6 was heated to a temperature of 2000°C. A deposition of filmy diamond having a thickness of about 5 μm on thesubstrate 5 was observed.

EXAMPLE 7

A surface-polished silicon wafer was used as the substrate 5 and agaseous mixture comprising trimethylamine [(CH₃)₃ N] and hydrogen at amixing ratio of 1:100 (volume ratio) was used as the reaction gas. Thepressure in the reaction tube was adjusted to 50 Torr and the substratetemperature was adjusted to 650° C. The growth was carried out for 1hour while the tungsten filament 6 was heated to a temperature of 2000°C. A deposition of filmy diamond having a thickness of about 3 μm on thesubstrate 5 was observed.

EXAMPLE 8

The same apparatus as in Examples 1 through 7 was used to producediamond, while varying conditions such as the kinds and flow rates ofgases for producing diamond, the substrate temperature, filamenttemperature, and the like. The flow speed of the gases is shown in Table1 in () and by units of SCCM (ditto, hereinafter).

                                      TABLE 1                                     __________________________________________________________________________                    Production Conditions                 Results                                 Volume Proportion of                                                                       Substrate                                                                             Pressure of      Deposition Speed              Kinds and Flow                                                                          Organic Compound Gases                                                                     Temperature                                                                           Reaction Gases                                                                        Temperature                                                                            of Diamond              Sample No.                                                                          Rates of Gases                                                                          to Hydrogen Gas                                                                            (°C.)                                                                          (Torr)  Filament (°C.)                                                                  (μm/hr)              __________________________________________________________________________    1     H.sub.2 (200)                                                                           0.02         650     100     2000     20                            CH.sub.3 COCH.sub.3 (4)                                                 2     H.sub.2 (100)                                                                           0.01         600     760     2000     20                            CH.sub.3 COCH.sub.3 (1)                                                 3     H.sub.2 (500)                                                                            0.002       750      50     2000     10                            CH.sub.3 COOCH.sub.3 (1)                                                4     H.sub.2 (100)                                                                           0.01         700      50     2000      6                            CH.sub.3 OH(1)                                                          5     H.sub.2 (500)                                                                            0.002       600      40     2000     10                            C.sub.2 H.sub.5 OH(1)                                                   6     H.sub.2 (100)                                                                           0.01         750     200     2300     15                            CH.sub.3 CHO(1)                                                         7     H.sub.2 (200)                                                                           0.02         800     760     2500     18                            (CH.sub.3).sub.2 CHOH(4)                                                8     H.sub.2 (100)                                                                           0.02         700     100     2200     14                            [(CH.sub.3).sub.2 CH].sub.2 O(2)                                        9     H.sub.2 (300)                                                                           0.05         750     760     2300     23                            C.sub.2 H.sub.5 OC.sub.2 H.sub.5 (15)                                   10    H.sub.2 (100)                                                                           0.02         750     760     2500     28                            [(CH.sub.3).sub.3 CO].sub.2 (2)                                         11    H.sub.2 (100)                                                                           0.01         650      50     2000      6                            (CH.sub.3).sub.3 N(1)                                                   12    H.sub.2 (100)                                                                           0.02         700     200     2300     10                            CH.sub.3 NH.sub.2 (2)                                                   13    H.sub.2 (100)                                                                           0.01         650      50     2000      7                            CH.sub.3 NNCH.sub.3 (1)                                                 14    H.sub.2 (100)                                                                           0.01         650     100     2000      8                            CH.sub.3 CONH.sub.2 (1)                                                 __________________________________________________________________________

EXAMPLE 9

A surface-polished silicon wafer was used as the substrate 5 shown inFIG. 2 and a gaseous mixture comprising acetone trimethylamine [(CH)₃ N]and hydrogen at a mixing ratio of 1:100 (volume ratio) was used as thereaction gas. The pressure in the reaction tube 4 was adjusted to 50Torr and the substrate temperature was adjusted to 550° C., and thetungsten filament 6 was heated at 2000° C. The surface of the substrate5 was irradiated with an electron beam at a current density of 10 mA/cm²and the growth was carried out for 1 hour. A deposition of filmy diamondhaving a thickness of about 2-3 μm on the substrate 5 was observed.

EXAMPLE 10

A surface-polished silicon wafer was used as the substrate 5 shown inFIG. 2 and a gaseous mixture comprising acetone (CH₃ COCH₃) and hydrogenat a mixing ratio of 1:100 (volume ratio) was used as the reaction gas.The pressure in the reaction tube 4 was adjusted to 50 Torr and thesubstrate temperature was adjusted to 750° C., and the tungsten filament6 was heated at 2000° C. The surface of the substrate 5 was irradiatedwith an electron beam at a current density of 10 mA/cm² and the growthwas carried out for 1 hour. A deposition of filmy diamond having athickness of about 25 μm on the substrate 5 was observed.

EXAMPLE 11

The same apparatus as in Examples 9 and 10 was used to produce diamond,while varying conditions such as the kinds and flow rates of gases forproducing diamond, the substrate temperature, pressure of reaction gas,current density, and the like.

                                      TABLE 2                                     __________________________________________________________________________                   Production Conditions             Results                                     Volume Proportion of                                                                       Substrate                                                                            Pressure of                                                                           Current                                                                             Deposition Speed                   Kinds and Flow                                                                         Organic Compound Gases                                                                     Temperature                                                                          Reaction Gases                                                                        Density                                                                             of Diamond                   Sample No.                                                                          Rates of Gases                                                                         to Hydrogen Gas                                                                            (°C.)                                                                         (Torr)  (Am/cm.sup.2)                                                                       (μm/hr)                   __________________________________________________________________________    15    H.sub.2 (100)                                                                          0.01         750     50      10   25                                 CH.sub.3 COCH.sub.3 (1)                                                 16    H.sub.2 (100)                                                                          0.02         650    760      30   25                                 CH.sub.3 COCH.sub.3 (2)                                                 17    H.sub.2 (100)                                                                          0.02         700    200     100   35                                 CH.sub.3 COCH.sub.3 (2)                                                 18    H.sub.2 (200)                                                                          0.05         650    100      10   20                                 CH.sub.3 OH(10)                                                         19    H.sub.2 (100)                                                                          0.01         650    100     200   32                                 CH.sub.3 CHO(1)                                                         20    H.sub.2 (100)                                                                          0.02         700    200     300   35                                 [(CH.sub.3).sub.3 CO].sub.2 (2)                                         21    H.sub.2 (100)                                                                          0.02         750    200     500   43                                 [(CH.sub.3).sub.3 CO](2)                                                22    H.sub.2 (100)                                                                          0.01         550    100      10    8                                 (CH.sub.3).sub.3 N(1)                                                   23    H.sub.2 (100)                                                                          0.01         650     50      30   12                                 (CH.sub.3).sub.2 NH(1)                                                  24    H.sub.2 (100)                                                                          0.04         700    200      10    8                                 CH.sub.3 NH(4)                                                          25    H.sub.2 (100)                                                                          0.02         700    200      10    7                                 CH.sub.3 CONH.sub.2 (2)                                                 26    H.sub.2 (100)                                                                          0.03         600    760      50   17                                 CH.sub.3 COC.sub.2 H.sub.5 (3)                                          27    H.sub.2 (100)                                                                          0.01         650    200     200   28                                 CH.sub.3 OCH.sub.3 (1)                                                  28    H.sub.2 (100)                                                                          0.01         700    200     300   30                                 (CH.sub.3 CO).sub.2 O(1)                                                29    H.sub.2 (400)                                                                          0.03         700    100     150   27                                 CH.sub.3 OOH(12)                                                        30    H.sub.2 (300)                                                                          0.02         750    300     300   43                                 (CH.sub.3).sub.3 COOH(6)                                                __________________________________________________________________________

EXAMPLE 12

A surface-polished silicon wafer was used as the substrate 5 shown inFIG. 3, and diamond was produced under the conditions as shown in Table3. Note, two kinds of lamps were used as the light source 14.

                                      TABLE 3                                     __________________________________________________________________________                Production Conditions                     Results                 Sam-        Volume Proportion of                                                                       Substrate                                                                            Pressure of                                                                           Kind of Power of                                                                            Deposition Speed        ple                                                                              Kinds and Flow                                                                         Organic Compound Gases                                                                     Temperature                                                                          Reaction Gases                                                                        Light Source                                                                          Light of Diamond              No.                                                                              Rates of Gases                                                                         to Hydrogen Gas                                                                            (°C.)                                                                         (Torr)  or Light                                                                              Source (W)                                                                          (μm/hr)              __________________________________________________________________________    31 H.sub.2 (100)                        Mercury Lamp                                                                          100                              CH.sub.3 COCH.sub.3 (5)                                                                0.05         650    10                    2.4                        Hg(0.1)                              Xenon Lamp                                                                            350                           32 H.sub.2 (100)                        Mercury Lamp                                                                          110                              CH.sub.3 COCH.sub.3 (2)                                                                0.02         700    50                    1.5                        Ar(3)                                Heavy Hydro-                                                                          200                                                                   gen Lamp                              33 H.sub.2 (50)                         Mercury Lamp                                                                          110                                       0.04         600    30                    0.3                        CH.sub.3 COCH.sub.3 (2)              Argon Reso-                                                                            24                                                                   nance Lamp                            34 H.sub.2 (100)                        Mercury Lamp                                                                          110                              CH.sub.3 COCH.sub.3 (3)                                                                0.04         650    100                   3.5                        Xe(3)                                Heavy Hydro-                                                                          200                                                                   gen Lamp                              35 H.sub.2 (50)                         Mercury Lamp                                                                          110                              CH.sub.3 COCH.sub.3 (3)                                                                0.06         600    50                    0.8                        C.sub.2 H.sub.2 (30)                 Heavy Hydro-                                                                          200                                                                   gen Lamp                              36 H.sub.2 (50)                         Mercury Lamp                                                                          110                              CH.sub.3 COCH.sub.3 (2)                                                                0.04         650    10                    2.0                        NH.sub.3 (50)                        Heavy Hydro-                                                                          200                                                                   gen Lamp                              37 H.sub.2 (50)                         Mercury Lamp                                                                          110                              CH.sub.3 COCH.sub.3 (1)                                                                0.02         650    20                    0.3                        C.sub.2 H.sub.6 (20)                 Heavy Hydro-                                                                          200                                                                   gen Lamp                              38 H.sub.2 (50)                         Mercury Lamp                                                                          110                              CH.sub.3 COCH.sub.3 (5)                                                                0.1          750     5                    1.6                        C.sub.2 H.sub.4 (30)                 Heavy Hydro-                                                                          200                                                                   gen Lamp                              39 H.sub.2 (100)                        Mercury Lamp                                                                          110                              CH.sub.3 COC.sub.2 H.sub.5 (2)                                                         0.02         650    100                   3.1                        Hg(0.1)                              Xenon Lamp                                                                            350                           40 H.sub.2 (50)                         Mercury Lamp                                                                          110                              CH.sub.3 OH(3)                                                                         0.06         700    20                    2.5                        Hg(0.05)                             Xenon Lamp                                                                            350                           41 H.sub.2 (50)                         Mercury Lamp                                                                          110                              CH.sub.3 CHO(2)                                                                        0.04         650    760                   4.6                        Hg(0.05)                             Xenon Lamp                                                                            350                           42 H.sub.2 (50)                         Mercury Lamp                                                                          110                              (CH.sub.3).sub.2 CHOH(3)                                                               0.06         650    10                    2.7                        Hg(0.05)                             Xenon Lamp                                                                            350                           43 H.sub.2 (100)                        Mercury Lamp                                                                          110                              [(CH.sub.3).sub.3 CO].sub.2 (2)                                                        0.02         600    760                   3.6                        Hg(0.1)                              Xenon Lamp                                                                            350                           44 H.sub.2 (100)                        Mercury Lamp                                                                          110                              CH.sub.3 CHO(2)                                                                        0.02         650     5                    1.6                        Xe(3)                                Heavy Hydro-                                                                          200                                                                   gen Lamp                              45 H.sub.2 (100)                        Mercury Lamp                                                                          110                              (CH.sub.3).sub.2 CHOH(3)                                                               0.03         700    20                    1.6                        Xe(3)                                Heavy Hydro-                                                                          200                                                                   gen Lamp                              46 H.sub.2 (100)                        Mercury Lamp                                                                          110                              [(CH.sub.3).sub.3 CO].sub.2 (2)                                                        0.02         750    200                   2.5                        Xe(3)                                Heavy Hydro-                                                                          200                                                                   gen Lamp                              47 H.sub.2 (100)                        Mercury Lamp                                                                          110                              CH.sub.3 NH.sub.2 (5)                                                                  0.05         750    100                   2.0                        Hg(0.1)                              Xenon Lamp                                                                            350                           48 H.sub.2 (100)                        Mercury Lamp                                                                          110                              (CH.sub.3).sub.3 N(3)                                                                  0.03         700    50                    3.1                        Hg(0.1)                              Xenon Lamp                                                                            350                           49 H.sub.2 (100)                        Mercury Lamp                                                                          110                              (CH.sub.3 N.sub.2)(4)                                                                  0.04         650    760                   4.7                        Hg(0.1)                              Xenon Lamp                                                                            350                           50 H.sub.2 (100)                        Mercury Lamp                                                                          110                              CH.sub.3 CONH.sub.2 (1)                                                                0.01         650    30                    1.8                        Hg(0.1)                              Xenon Lamp                                                                            350                           51 H.sub.2 (100)                        Mercury Lamp                                                                          110                              CH.sub.3 NO.sub.2 (2)                                                                  0.02         650    10                    1.2                        Hg(0.1)                              Xenon Lamp                                                                            350                           __________________________________________________________________________

EXAMPLE 13

A surface-polished silicon wafer was admitted in an electric dischargingapparatus provided with opposing targets, and the growth of diamond wascarried out for one hour under the conditions described below. Thesubstrate 5 is shown in FIG. 4 and the conditions for producing diamondare shown in Table 4.

                                      TABLE 4                                     __________________________________________________________________________                 Production Conditions                    Results                              Kinds of and                                                                          Volume Proportion of                                                                       Substrate                                                                            Pressure of                                                                           Power                                                                              Deposition Speed        Sample       Flow Rates of                                                                         Orgainc Compound Gases                                                                     Temperature                                                                          Reaction Gases                                                                        Density                                                                            of Diamond              No. Discharge                                                                              Gases   to Hydrogen Gas                                                                            (°C.)                                                                         (Torr)  (W/cm.sup.2)                                                                       (μm/hr)              __________________________________________________________________________    52  Direct Current                                                                         H.sub.2 (100)                                                                         0.02         750     20      30  14                          Glow Discharge                                                                         CH.sub.3 COCH.sub.3 (2)                                          53  Direct Current                                                                         H.sub.2 (100)                                                                         0.01         700     5       20  15                          Glow Discharge                                                                         C.sub.2 H.sub.5 OH(1)                                            54  Direct Current                                                                         H.sub.2 (100)                                                                         0.01         700     10      50  18                          Glow Discharge                                                                         [(CH.sub.3).sub.3 CO].sub.2 (1)                                  55  Direct Current                                                                         H.sub.2 (100)                                                                         0.01         750     10      30  12                          Glow Discharge                                                                         (CH.sub.3).sub.3 N(1)                                            56  Direct Current                                                                         H.sub.2 (100)                                                                         0.01         750    760     1500 35                          Arc Discharge                                                                          CH.sub.3 COCH.sub.3 (1)                                          57  Direct Current                                                                         H.sub.2 (100)                                                                         0.01         750    200      300 30                          Arc Discharge                                                                          CH.sub.3 CHO(1)                                                  58  Direct Current                                                                         H.sub.2 (100)                                                                         0.01         750    800     1700 42                          Arc Discharge                                                                          [(CH.sub.3).sub.3 CO].sub.2 (1)                                  59  Direct Current                                                                         H.sub.2 (100)                                                                         0.01         650    760     1500 27                          Arc Discharge                                                                          (CH.sub.3).sub.3 NH(1)                                           60  Alternating                                                                            H.sub.2 (100)                                                                         0.01         700    760     1000 31                          Current Arc                                                                            CH.sub.3 COCH.sub.3 (1)                                              Discharge                                                                 61  Alternating                                                                            H.sub.2 (100)                                                                         0.02         750    760      900 23                          Current Arc                                                                            CH.sub.3 OH(2)                                                       Discharge                                                                 62  Alternating                                                                            H.sub.2 (100)                                                                         0.01         600    760     1000 29                          Current Arc                                                                            C.sub.2 H.sub.5 OC.sub.2 H.sub.5 (1)                                 Discharge                                                                 63  Alternating                                                                            H.sub.2 (100)                                                                         0.01         650    760     1000 40                          Current Arc                                                                            [(CH.sub.3).sub.3 CO].sub.2 (1)                                      Discharge                                                                 64  Alternating                                                                            H.sub.2 (100)                                                                         0.01         650    760     1200 25                          Current Arc                                                                            (CH.sub.3).sub.3 N(1)                                                Discharge                                                                 __________________________________________________________________________

CAPABILITY OF EXPLOITATION IN INDUSTRY

As is apparent from the foregoing description, the following prominenteffects can be attained according to the present invention.

(a) Since the number of kinds of starting gases that can be used in thepresent invention is much larger than in the conventional methods, thepresent invention is very advantageous from the practical viewpoint.

(b) Continuous production is possible and the apparatus and startingmaterial costs are very cheap.

(c) Since the range of the synthesis conditions is broad, the synthesiscan be carried out very easily.

(d) The speed of deposition of diamond is several times to scores oftimes as high as the precipitation speeds in the conventional methods,and granular or filmy diamond having a high quality can be obtained.

I claim:
 1. A synthesizing process for diamond by a chemical vapor phasegrowth method, characterized by converting an organic compoundcontaining carbon, hydrogen and at least one of oxygen and nitrogen, toa gas phase, mixing the gas with hydrogen gas, decomposing the mixed gasby an energy of heat, electron beam, light, direct current glowdischarge, alternating current glow discharge, or direct current arcdischarge, and introducing the decomposed gas to the surface of a heatedsubstrate to deposit diamond on the surface of the substrate.
 2. Asynthesizing process according to claim 1, wherein the heat for saiddecomposition is generated by a heater heated to a temperature of from1500° C. to 2800° C.
 3. A synthesizing process according to claim 1,wherein the electron beam for said decomposition has a current densityof not less than 1 mA/cm².
 4. A synthesizing process according to claim1, wherein the light for decomposition has a wavelength of not more than600 nm.
 5. A synthesizing process according to claim 1, wherein theelectric discharge for said decomposition is carried out at a powerdensity of not less than 1 W/cm².
 6. A synthesizing process according toany one of claims 1 through 5, wherein the pressure of a reaction tube,in which said decomposition is carried out, is from 0.01 to 1000 Torr.